During the last year, it's become clear that multifamily owners and operators have been using concessions to draw renters in. But a new report from Moody's Analytics suggests that the use is broader and effective rents are taking a hit.

Effective rents, Moody's points out, are not one of the typical metrics those in the industry use to judge performance, either of an individual property or collectively for the market. And yet, they are important. Provide concessions and the result may something that strengthens a mutual relationship to the benefit of each.

It's a trend that has expanded. "The growing divergence between asking and effective rents indicates that landlords, confronted with rising vacancies, are offering larger concessions to attract tenants," Moody's wrote. This trend suggests that in periods of high vacancy, the balance of power in lease negotiations may shift towards tenants, as landlords are more motivated to fill their spaces. Rising vacancies can create opportunities for tenants to secure more favorable lease terms."